Novel potential lncRNA biomarker in B cells indicates essential pathogenic pathway activation in patients with SLE.

OBJECTIVES: Systemic lupus erythematosus (SLE) is a highly heterogeneous disease, and B cell abnormalities play a central role in the pathogenesis of SLE. Long non-coding RNAs (lncRNAs) have also been implicated in the pathogenesis of SLE. The expression of lncRNAs is finely regulated and cell-type dependent, so we aimed to identify B cell-expressing lncRNAs as biomarkers for SLE, and to explore their ability to reflect the status of SLE critical pathway and disease activity. METHODS: Weighted gene coexpression network analysis (WGCNA) was used to cluster B cell-expressing genes of patients with SLE into different gene modules and relate them to clinical features. Based on the results of WGCNA, candidate lncRNA levels were further explored in public bulk and single-cell RNA-sequencing data. In another independent cohort, the levels of the candidate were detected by RT-qPCR and the correlation with disease activity was analysed. RESULTS: WGCNA analysis revealed one gene module significantly correlated with clinical features, which was enriched in type I interferon (IFN) pathway. Among non-coding genes in this module, lncRNA RP11-273G15.2 was differentially expressed in all five subsets of B cells from patients with SLE compared with healthy controls and other autoimmune diseases. RT-qPCR validated that RP11-273G15.2 was highly expressed in SLE B cells and positively correlated with IFN scores (r=0.7329, p<0.0001) and disease activity (r=0.4710, p=0.0005). CONCLUSION: RP11-273G15.2 could act as a diagnostic and disease activity monitoring biomarker for SLE, which might have the potential to guide clinical management.

Integrative Functional Genomics Identifies Systemic Lupus Erythematosus Causal Genetic Variant in the IRF5 Risk Locus.

OBJECTIVE: IRF5 plays a crucial role in the development of lupus. Genome-wide association studies have identified several systemic lupus erythematosus (SLE) risk single-nucleotide polymorphisms (SNPs) enriched in the IRF5 locus. However, no comprehensive genome editing-based functional analysis exists to establish a direct link between these variants and altered IRF5 expression, particularly for enhancer variants. This study was undertaken to dissect the regulatory function and mechanisms of SLE IRF5 enhancer risk variants and to explore the utilization of clustered regularly interspaced short palindromic repeat interference (CRISPRi) to regulate the expression of disease risk gene to intervene in the disease. METHODS: Epigenomic profiles and expression quantitative trait locus analysis were applied to prioritize putative functional variants in the IRF5 locus. CRISPR-mediated deletion, activation, and interference were performed to investigate the genetic function of rs4728142. Allele-specific chromatin immunoprecipitation-quantitative polymerase chain reaction and allele-specific formaldehyde-assisted isolation of regulatory element-quantitative polymerase chain reaction were used to decipher the mechanism of alleles differentially regulating IRF5 expression. The CRISPRi approach was used to evaluate the intervention effect in monocytes from SLE patients. RESULTS: SLE risk SNP rs4728142 was located in an enhancer region, indicating a disease-related regulatory function, and risk allele rs4728142-A was closely associated with increased IRF5 expression. We demonstrated that an rs4728142-containing region could act as an enhancer to regulate the expression of IRF5. Moreover, rs4728142 affected the binding affinity of zinc finger and BTB domain-containing protein 3 (ZBTB3), a transcription factor involved in regulation. Furthermore, in monocytes from SLE patients, CRISPR-based interference with the regulation of this enhancer attenuated the production of disease-associated cytokines. CONCLUSION: These results demonstrate that the rs4728142-A allele increases the SLE risk by affecting ZBTB3 binding, chromatin status, and regulating IRF5 expression, establishing a biologic link between genetic variation and lupus pathogenesis.